Victorian Police are scrambling to protect informants and their own officers after the leaking of hundreds of sensitive documents allegedly by a junior officer. A former NSW police assistant commissioner Clive Small says corruption in the Victorian force is not systemic but appears every few years with the leaking of information that sometimes ends in murder.

Transcript

TONY EASTLEY: Victorian police are scrambling to protect their informants and officers after what the chief commissioner described as the "gravest" security breach he's ever seen.

Hundreds of vital police documents detailing investigations have been discovered in raids on three properties, including one linked to outlaw motorcycle gangs.

A junior officer has been suspended and is expected to face criminal charges over the leak.

Here's Samantha Donovan.

SAMANTHA DONOVAN: The chief commissioner of Victoria Police Ken Lay says the massive leak of sensitive documents has left the lives of informants and officers at risk.

Clive Small is a former assistant commissioner of the New South Wales police. He says police corruption in Victoria seems to follow a particular pattern.

CLIVE SMALL: What we see in Victoria is every few years, is a case of the very serious leaking of information which often results in murder.

SAMANTHA DONOVAN: Taskforce Keel has been set up to investigate the leak and identify who may be at risk.

Clive Small says the police will need to be careful about how they warn informants of a possible risk to their safety.

CLIVE SMALL: You have to be careful how you time these approaches because you approach someone while you're in the early stages of an investigation, give them a warning, they might then repeat that warning to other people and that blows your investigation. So there is a balancing act all the way though this about how do you make sure that you have a successful investigation by stopping the leaks and also maintaining the welfare and wellbeing of your informant.

SAMANTHA DONOVAN: Do you think though that Victoria Police will now have trouble maintaining informants and cultivating new ones because of the leak?

CLIVE SMALL: Oh look I think some will keep coming forward. The risk you have here is that if there are people who have been informants over a lengthy period of time and been, if we can say, informants providing very useful information, I think the risk is you might lose some of them.

SAMANTHA DONOVAN: Clive Small says one of the biggest questions to be answered is how a junior officer allegedly managed to get hold of such vital information and just how widely it's been spread.

CLIVE SMALL: We understand that copies of the documents have been recovered. But who else has been told about the information? How widely know is it amongst the criminal fraternity? What lives are at risk? What police operations are at risk? Have they been photocopied, or more likely has the information simply been shared around to other people that are associated with this group?

CLIVE SMALL: These long-term strategies are quite sophisticated, cost a lot of money or other investments. And I'm not too sure that bikie gangs think and plan five and six and seven years down the track.